The object is to define central effects of narcotic antagonists in man. The first drug to be studied is naltrexone. The main issue is the capability of this compound to block acute effects of heroin. The methods will include pupillography, respiratory rate, electroencephalography, contingent negative variation, performance on an auditory detection task, and subjective reports. The results should provide data for rationalization of pharmacological treatment of opiate addiction. The effects of methadone will also be studied, using the methods outlined above.